1. Field of the Invention
This invention relates to a composition for dielectric porcelain, and a dielectric porcelain and a capacitor by use of the composition.
2. Related Background Art
Heretofore, there have been employed as the dielectric member to be used for capacitors, etc. porcelains comprising BaTiO.sub.3, BaSnO.sub.3, CaTiO.sub.3 or a solid solution having other components added to these double oxides as the main component, or these materials modified with various additives. However, these porcelains are required to be fired at a high temperature of 1300.degree. to 1400.degree. C. and therefore, for example, when applied for a laminated capacitor, there ensues the problem that no silver type electrode can be used as the internal electrode, and it has been sought to develop a porcelain which can be fired at lower temperatures.
Also, in the dielectric porcelain of the prior art, if the dielectric constant at around normal temperature is made greater, the temperature dependent rate of change in dielectric constant becomes also greater; on the contrary, if the temperature dependent rate of change in dielectric constant at around normal temperature is made smaller, the dielectric constant also becomes smaller. Thus, it has been difficult to obtain a porcelain with a great dielectric constant and a small temperature dependent rate of change in dielectric constant.
Further, in the case when the porcelain has high dielectric property, the Curie point becomes around normal temperature due to modification with an additive, whereby mechanical strength will be lowered due to phase transition at this temperature, and there is also involved the problem that it can be used as a functional element with difficulty.